Wandering up to bet on defeat (7)
I believe the answer is:
outplay
'defeat' is the definition.
(I know that outplay is a more specific form of the action beat)
'wandering up to bet' is the wordplay.
'wandering' indicates anagramming the letters.
'bet' becomes 'lay' (lay bet is a type of bet in gambling).
'up'+'to'='upto'
'upto' anagrammed gives 'outp'.
'outp'+'lay'='OUTPLAY'
'on' acts as a link.
(Other definitions for outplay that I've seen before include "Perform better than" , "Excel at games" , "Defeat (sport)" , "Get the better of" , "As sportsperson, overcome" .)